Disposable components for reusable physiological sensor

ABSTRACT

A sensor cartridge according to embodiments of the disclosure is capable of being used with a non-invasive physiological sensor. Certain embodiments of the sensor cartridge protect the sensor from damage, such as damage due to repeated use, reduce the need for sensor sanitization, or both. Further, embodiments of the sensor cartridge are positionable on the user before insertion in the sensor and allow for improved alignment of the treatment site with the sensor. In addition, the sensor cartridge of certain embodiments of the disclosure can be configured to allow a single sensor to comfortably accommodate treatment sites of various sizes such as for both adult and pediatric applications.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 15/864,389, filed Jan. 8, 2018, which application is acontinuation of U.S. patent application Ser. No. 14/626,570, filed Feb.19, 2015, which application is a continuation of U.S. patent applicationSer. No. 12/782,651, filed May 18, 2010, which application claims thebenefit of priority from U.S. Provisional Application No. 61/179,670,filed May 19, 2009. The entire contents of each of the above items arehereby incorporated by reference herein for all purposes.

FIELD OF THE DISCLOSURE

The present disclosure generally relates to disposable components ofnon-invasive physiological sensors.

BACKGROUND OF THE DISCLOSURE

Non-invasive physiological sensors are applied to the body formonitoring or making measurements indicative of a patient's health. Oneapplication for a non-invasive physiological sensor is pulse oximetry,which provides a noninvasive procedure for measuring the oxygen statusof circulating blood. Oximetry has gained rapid acceptance in a widevariety of medical applications, including surgical wards, intensivecare and neonatal units, general wards, and home care and physicaltraining. A pulse oximetry system generally includes a physiologicalsensor having light emitters and a detector, such as one or more LEDsand a light sensor. The sensor is attached to a tissue site, such as afinger, toe, ear lobe, nose, hand, foot, or other site having pulsatileblood flow which can be penetrated by light from the emitters. Thedetector is responsive to the emitted light after attenuation bypulsatile blood flowing in the tissue site. The detector outputs adetector signal to a monitor which processes the signal to provide anumerical readout of physiological parameters such as oxygen saturation(SpO2) and pulse rate.

High fidelity pulse oximeters capable of reading through motion inducednoise are disclosed in U.S. Pat. Nos. 6,770,028, 6,658,276, 6,157,850,6,002,952 5,769,785, and 5,758,644, which are assigned to MasimoCorporation (“Masimo”) and are incorporated by reference herein.Advanced physiological monitoring systems may incorporate pulse oximetryin addition to advanced features for the calculation and display ofother blood parameters, such as carboxyhemoglobin (HbCO), methemoglobin(HbMet) and total hemoglobin (Hbt), total Hematocrit (Hct), oxygenconcentrations and glucose concentrations, as a few examples. Advancedphysiological monitors and corresponding multiple wavelength opticalsensors capable of measuring parameters in addition to SpO2, such asHbCO, HbMet and Hbt are described in at least U.S. patent applicationSer. No. 11/367,013, filed Mar. 1, 2006, titled Multiple WavelengthSensor Emitters and U.S. patent application Ser. No. 11/366,208, filedMar. 1, 2006, titled Noninvasive Multi-Parameter Patient Monitor,assigned to Masimo Laboratories, Inc. and incorporated by referenceherein. Further, noninvasive blood parameter monitors and opticalsensors including Rainbow™ adhesive and reusable sensors and RAD-57™ andRadical-7™ monitors capable of measuring SpO2, pulse rate, perfusionindex (PI), signal quality (SiQ), pulse variability index (PVI), HbCOand HbMet, among other parameters, are also commercially available fromMasimo.

SUMMARY OF THE DISCLOSURE

Optical sensors are widely used across clinical settings, such asoperating rooms, emergency rooms, post anesthesia care units, criticalcare units, outpatient surgery and physiological labs, to name a few.Use in these settings exposes sensors, and in particular reusablesensors, to the potential risks of contamination and the resultingspread of nosocomial (hospital-acquired) infections. Studies havesuggested that visual inspection of sensors may not detectcontamination. Further, while a low-level disinfection protocol ofalcohol wipes, dilute bleach scrubs or distilled water wipes can beeffective when done correctly, reusable sensors may still be at risk forbacteria including MRSA (methicillin resistant Staphylococcus aureus).MRSA causes skin infections and can occasionally spread to almost anyother organ in the body, sometimes with life-threatening potential. Itis therefore a priority among medical care facilities to preventcontamination of reusable sensors by foreign and infectious materialsand to prevent the spread of nosocomial infections. A sterile sensorcover advantageously provides a sterile environment without interferingwith sensor functionality and capability. For example, the sterilesensor cover may be substantially impermeable to infectious agents(e.g., bacteria) and substantially optically transparent ortransmissive.

Further, sensor elements such as the detector, emitters and associatedcircuitry can be expensive parts of a patient monitoring system. Often,relatively inexpensive degradable portions of the sensor become damageddue to repeated use or frequent sterilization. For example, the portionsof the sensor which contact the user's skin often become soiled ordamaged after each use. In such cases, users often disconnect the sensorcable from the monitor and replace the entire sensor. Moreover, incertain cases, such as for portable applications, it is useful for asensor to be integrated into the patient monitor housing and not beattached by a cable. In such cases the sensor may not be removable fromthe monitor.

Other attempted solutions that include sensors with flexible, adhesivesubstrates having disposable and reusable portions. The disposableportion generally includes the adhesive portion of the sensor, which canlose its tack. Such sensors generally wrap around and adhesively attachto the tissue site. However, non-adhesive sensors having rigid housings,such as clip type sensors which clamp onto the tissue of the patient,are also commonly used in pulse oximetry and other patient monitoringapplications. These sensors include degradable components that canbecome damaged or soiled due to frequent use, such as upper and lowerpads which contact the user's skin.

It is therefore desirable to decouple the degradable portions from therest of the sensor so that the degradable portions can be replaced in acost-effective manner, and the rest of the sensor can be reused. Adisposable sensor cartridge according to embodiments of the disclosureis capable of being used with a non-invasive physiological sensor andprotects the sensor from damage due to repeated use or sterilization.

In addition, incorrect alignment of a patient's tissue site with thesensor elements can lead to inaccurate results. For example, where thetissue site is a patient's finger, the emitter and detector shouldgenerally be aligned with the nail bed of the patient. Often it isdifficult to determine whether the sensor is properly aligned because,for example, the sensor housing impedes the view of the tissue site inrelation to the emitter and detector. In such cases, it may take theoperator a significant amount of time to realize that a sensor ismisaligned. As such, there is a need for a sensor which provides forrobust tissue site alignment. Embodiments of the sensor cartridge arepositionable on the user before placing the treatment site in thesensor, allowing for improved alignment of the treatment site.

In order to provide cost savings and allow for efficient use, it is alsoadvantageous to be able to reuse sensors on different patients havingtissue sites of various sizes, such as for both adults and children. Thesensor cartridge of certain embodiments can be configured to allow asensor to comfortably accommodate treatment sites of various sizes, suchas for both adult and pediatric applications.

According to certain embodiments, a disposable sensor cartridge isprovided for use with a noninvasive physiological sensor. The sensorcartridge can be capable of attaching to a tissue site and mating with ahousing of the sensor. In certain embodiments, the sensor cartridgecomprises a first portion comprising a first aperture configured toallow light emitted from one or more emitters of the sensor to travelthrough the first aperture such that the light is incident on a firstregion of a tissue site and travels through and is attenuated by bodytissue of the tissue site. The attenuated light may exit the tissue siteat a second region of the tissue site. In certain embodiments, thesensor cartridge also includes a second portion comprising a secondaperture configured to allow the attenuated light to travel through thesecond aperture and to be received by a detector of the sensor. In someembodiments, the first and second portions coupled to define a cavitycapable of receiving the tissue site. In certain embodiments, the sensorcartridge can also include an electrical component capable of electricalcommunication with the sensor. In some embodiments, the first portion isin contact with the first region while the cartridge is attached to thetissue site and the second portion is in contact with the second regionwhile the cartridge is attached to the tissue site.

According to an aspect of the disclosure, a method of using anoninvasive physiological sensor having a housing is provided. Themethod can include providing a disposable sensor cartridge comprising afirst portion comprising a first aperture and a second portioncomprising a second aperture. In certain embodiments, the disposablesensor cartridge can also include an electrical component. The firstportion and second portion may together define a cavity capable ofreceiving the tissue site. In certain embodiments, the method furtherincludes attaching the sensor cartridge to the tissue site such that thetissue site is disposed within the cavity. The method according to someembodiments also includes mating the sensor cartridge with the sensorsuch that the sensor cartridge is disposed within a cavity of the sensorhousing. In certain embodiments, mating of the sensor cartridge with thesensor is such that the electrical component is in electricalcommunication with a portion of the sensor.

In certain embodiments, a disposable sterile barrier is provided. Thedisposable sterile barrier may interpose a material impermeable toinfectious biological substances between a tissue site and surfaces of asensor configured to grasp the tissue site. The sensor may be configuredto transmit optical radiation into the tissue site and to generate asignal responsive to the optical radiation after attenuation bypulsatile blood flow within the tissue site. In certain embodiments, thedisposable sterile barrier comprises an optically transparent materialthat is substantially impermeable to infectious biological substances.The disposable barrier may comprise a first portion of the materialformed such that the first portion can be interposed between a tissuesite and a first surface of a reusable optical sensor proximate anemitter of the sensor. In certain embodiments, the disposable barriermay comprise a second portion of the material formed such that thesecond portion can be interposed between the tissue site and a secondsurface of the sensor proximate a detector of the sensor.

In certain embodiments, an optical sensing method of non-invasivelymeasuring the constituents of pulsatile blood flow within a tissue sitewithout substantial risk nosocomial infection by direct contact betweena sensor and the tissue site. The optical sensing method may includeproviding a reusable optical sensor having an emitter disposed within afirst housing and a detector disposed within a second housing, theemitter and detector in communication with a sensor cable, the first andsecond housings configured to be urged against opposite sides of atissue site upon application of the sensor to the tissue site, theemitter configured to transmit optical radiation having one or morepredetermined wavelengths into the tissue site and the detectorconfigured to receive the optical radiation after attenuation by thetissue site. The sensor may be configured to generate one or moresignals indicative of the attenuated radiation, the one or more signalstransmitted via the sensor cable to a monitor configured to process theone or more signals to determine one or more physiological parameters ofpatient. The method may include applying a barrier so as to makephysiological measurements without direct contact between the tissuesite and the sensor. The barrier can be interposed between the tissuesite and the first housing and interposed between the tissue site andthe second housing upon application of the tissue site to the sensor,the barrier comprising material substantially impermeable to infectioussubstances and substantially transparent so as not to substantiallydistort the physiological measurements.

According to certain aspects of the disclosure, a disposable sterilebarrier is provided comprising an elongate tube comprising a cavity. Theelongate tube may comprise an open end and a closed end. In certainembodiments, the open end comprises an opening large enough toaccommodate a reusable optical sensor. The cavity can be sized to fullyenclose the reusable optical sensor and at least a portion of a sensorcable extending from the optical sensor. In some embodiments, theelongate tube comprises a material which is substantially opticallytransparent and substantially impermeable to infectious biologicalsubstances. In certain embodiments, the disposable sterile barrier mayfurther include a fastener disposed proximate the open end of theelongate tube and configured to seal the open end of the elongate tubearound the sensor cable.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a sensor cartridge and associated sensoraccording to an embodiment of the disclosure;

FIGS. 2A-D are side hinged-open, side hinged-closed, top and bottomperspective views, respectively, of the sensor cartridge of FIG. 1;

FIGS. 3A-D are side hinged-open and side hinged-closed views, top andbottom perspective views, respectively, of a sensor cartridge accordingto another embodiment of the disclosure;

FIG. 4 illustrates the mating of the sensor cartridge of FIG. 3 with asensor.

FIGS. 5A-B illustrate side views of two sensor cartridges of differingsizes according to an embodiment of the disclosure.

FIGS. 6A-B illustrate side views of two sensor cartridges of differingsizes according to another embodiment of the disclosure.

FIG. 7 is a side perspective view of a generally boot-shaped enclosureembodiment of a sterile sensor cover;

FIG. 8 is a side perspective view of a generally tube-shaped enclosureembodiment of a sterile sensor cover;

FIGS. 9A-F illustrate enclosing a reusable sensor with the boot-shapedenclosure and sealing the end with an attached tie; and

FIGS. 10A-E illustrate enclosing a reusable sensor with the tube-shapedenclosure and sealing the end with an adhesive strip.

FIGS. 11A-B illustrate top front and bottom rear perspective views,respectively, of a sensor cartridge according to an embodiment of thedisclosure.

FIGS. 12A-B illustrate top front and bottom rear perspective views,respectively, of a sensor cartridge according to another embodiment ofthe disclosure.

DETAILED DESCRIPTION

A sensor cartridge according to embodiments of the disclosure is capableof being used with a non-invasive physiological sensor. Certainembodiments of the sensor cartridge protect the sensor from damage, suchas damage due to repeated use, reduce the need for sensor sanitization,or both. Further, embodiments of the sensor cartridge are positionableon the user before insertion in the sensor and allow for improvedalignment of the treatment site with the sensor. In addition, the sensorcartridge of certain embodiments of the disclosure can be configured toallow a single sensor to comfortably accommodate treatment sites ofvarious sizes such as for both adult and pediatric applications. Theterms “sensor cover” and “sensor cartridge” are used throughout todescribe various embodiments of the disclosure. The terms may be usedinterchangeably and are not intended to be limiting.

The tissue site of the illustrated embodiments is a finger and thefollowing description therefore refers specifically to the tissue siteas a finger for the purposes of clarity. This is not intended to belimiting and, as described herein, the sensor cartridge 110 of certainembodiments may be used with other types of tissue sites.

FIG. 1 is a perspective view of a sensor cartridge 110 and associatedsensor 120 according to an embodiment of the disclosure. A user canplace a cartridge 110 on a finger of the patient and then insert thefinger along with the attached cartridge 110 into a non-invasivephysiological sensor 120.

The sensor 120 can be a clip-type sensor including an upper housing 122,a lower housing 124 and a hinge element 126. The upper and lowerhousings 122, 124 house electrical and/or optical components (not shown)of the non-invasive physiological sensor 120. For example, the upper andlower housings 122, 124 may house light emitters and a detector of apulse oximeter sensor, such as one or more LEDs and a light sensor. Thesensor 120 can be connected to a patient monitor (not shown) via a cable128. For example, the detector outputs a signal to the monitor over thecable 128 which then processes the signal to provide a numerical readoutof physiological parameters such as oxygen saturation (SpO2) and pulserate.

After placing the sensor cartridge 110 on the finger, the user canattach the sensor 120 to the patient by applying pressure to the ends123, 125 of the upper and lower housings 122, 124, forming a cavity 129capable of receiving the tissue site. Once the patient inserts thetissue site along with the attached sensor cartridge 110 into the cavity129, the pressure on the ends 123, 125 can be released such that theupper and lower housings 122, 124 come in contact with and secure thetissue site, allowing for accurate non-invasive physiologicalmeasurement.

Although disclosed with reference to the sensor of FIG. 1, an artisanwill recognize from the disclosure herein a wide variety of oximetersensors, optical sensors, noninvasive sensors, medical sensors, or thelike that may benefit from the sensor cartridges disclosed herein. Thesensor may not be a hinge type sensor but may instead, for example,include an integral housing having an annular ring type opening throughwhich the patient inserts their finger. In various embodiments, thesensor may be adapted to receive a tissue site other than a finger suchas a, toe, ear lobe, nose, hand, foot, or other site having pulsatileblood flow which can be penetrated by light from the emitter. Inaddition, the cartridge 110 may be used with a portable monitor andassociated sensor components in certain embodiments. Such monitors,including the sensor components, can be integrated into a hand-helddevice such as a PDA and typically do not include cables or separatemonitors. Portable monitors are often used by first responders inemergency situations, in part because of their portability and ease ofuse. As such, disposable cartridges 110 which can protect the sensorcomponents according to embodiments herein can be of particular benefitwhen used with spot-check monitors. In addition, in emergency situationsmedical personnel must treat a large number of patients relativelyquickly and it may therefore be difficult to sanitize sensors betweenpatients. Disposable cartridges 110 described herein benefit medicalpersonnel in such cases because a separate pre-sterilized cartridge 110can be used for each patient.

Referring still to FIG. 1, the cartridge 110 includes an upper portion114, a lower portion 116 and a hinge portion 112 which together form acavity 118 capable of receiving a finger. The upper portion 114, lowerportion 116 and hinge portion 112 are generally curved so as toaccommodate the natural shape of the finger. A hinge cut-out 113 can bedisposed on either side of the cartridge 110 near the hinge portion 112,allowing for the upper and lower portions 114, 116 to separate from eachother by rotating about the hinge portion 112. To apply the cartridge tothe finger, the upper portion 114 and lower portion 116 may be separatedsuch that they rotate about the hinge portion 112 and the cavity 118becomes large enough to comfortably receive the finger. Once the fingeris placed in the cavity 118, the upper and lower portions 114, 116 arereleased, coming into contact with and releasably attaching to thefinger. For example, in certain embodiments, the hinge portion 112 mayprovide a spring force which is transferred to the upper and lowerportions 114, 116 when they are released such that they grab onto thefinger. In some embodiments, the interior surface 119 of the cartridge110 may include an adhesive substance such that the cartridge 110 isreleasably attached to the finger or other tissue site. In otherconfigurations, the cartridge 110 simply rests on the finger and thereis not a separate attachment mechanism.

The upper portion 114 includes an upper aperture 115 and the lowerportion 116 includes a lower aperture 117. The apertures 115, 117generally allow for proper sensor operation. For example, the apertures115, 117 allow for light from one or more emitters of the sensor 120 tocontact the finger and for light attenuated by the tissue site to bereceived by a detector of the sensor 120.

Because the upper and lower sensor housings 122, 124 are often opaque,it can be difficult to determine whether or not a finger is properlyaligned once it is placed in the sensor. The apertures 115, 117 canallow for proper alignment of the sensor cartridge 110 with respect tothe finger prior to inserting the cartridge 110 and finger into thesensor 120. Proper alignment of the cartridge 110 with the finger cantherefore improve the accuracy of measurements by helping to ensure thatthe finger will be properly aligned with respect to the sensor 120elements upon mating of the cartridge 110 and sensor 120. In certaincases, medical personnel may not realize that an inaccurate measurementhas occurred, or may not realize it until after an alarm on the sensorgoes off, after removal of the sensor or after the patient has left thetreatment facility. As such, proper alignment can also help reduce costand save time.

The upper aperture 115 allows a user to visually determine whether thenail bed of a finger is properly aligned with the aperture 115. Properalignment of the nail bed also ensures that the lower aperture 117 isproperly aligned with the fleshy part of the underside of the finger. Inaddition, the user may visually determine that the underside of thefinger is properly aligned by looking through the lower aperture 117.The finger with the properly aligned cartridge 110 can then be insertedinto the sensor 120 such that the light from the emitters of the sensor120 will be incident on the nail bed through the upper aperture 115.Further, the detector of the sensor 120 then receives attenuated lightfrom the appropriate portion of the underside of the finger through thelower aperture 117. In other embodiments, the emitter of the sensor 120is housed in the lower housing 124 and the detector is housed in theupper housing 122.

In certain embodiments, a film or other material (not shown) may beincluded in one or more of the apertures 115, 117. For example, in oneembodiment, translucent plastic film is placed in the apertures 115, 117such that the properties of the emitted and attenuated light passingthrough the apertures are not affected by the material. In otherembodiments, material is used which does affect the optical properties.For example, an optical film which filters out particular wavelengths oflight is used in some embodiments.

Tactile feedback elements (not shown) may indicate proper alignment ofthe cartridge instead of, or in addition to, the apertures 115, 117. Forexample, one or more of the upper and lower portions 114, 116 mayinclude small protrusions which indicate to the patient whether thecartridge 110 is properly aligned. In one embodiment, for example,protrusions on either side of the finger indicate to the patient thatthe cartridge 110 is centered on the finger and a protrusion near thehinge portion 112 indicates that the finger is inserted appropriatelydeep into the cartridge 110. Other tactile elements such as, forexample, recesses, may be used in other embodiments.

In certain embodiments, the properties of the interior 119 of thecartridge 110 allow for proper and efficient calibration of the sensor120. For example, the interior 119 of the cartridge may be a highlyreflective color such as white. The interior 119 may also have a glossytexture in certain embodiments, which can also aid in the calibration ofthe sensor.

As discussed, the sensor cartridge 110 is configured to mate with thesensor 120. For example, the cartridge 110 of FIG. 1 mates in a frictionfit with the sensor 120. To release the cartridge 110 from the sensor120 after use, the user opens the sensor 120 clip, thereby relieving thepressure on the cartridge and tissue site from the upper and lowerhousings 122, 124. The user can then readily pull the tissue site andcartridge 110 out of the cavity 129. As will be appreciated by skilledartisans from the disclosure provided herein, other types of mating andrelease mechanisms are possible. For example, snap-fit matingconfigurations such as the one described below with respect to FIG. 3can be used. In some embodiments, a male or female track on thecartridge 110 fits into a corresponding male or female track on thesensor 120, as appropriate. A button or lever release mechanism may beused in certain embodiments. In some embodiments, the cartridge 110 mayautomatically release when the sensor 120 clip is opened.

The sensor cartridge 110 or a portion thereof can be constructed ofurethane rubber plastic in certain embodiments. In various otherconfigurations, as will be appreciated from the disclosure herein, thecartridge 110 may be made of other appropriate materials such asAcrylonitrile Butadiene Styrene (“ABS”) or other types of rubber orplastic materials. The cartridge 110 is formed with biodegradablematerial in certain embodiments.

The general structure of the sensor cartridge 110 may differ in variousconfigurations. For example, the cartridge may not be an integral moldedpiece as shown in the embodiment of FIG. 1 and may instead includeseparate pieces as discussed with respect to FIG. 3 below.

In an example scenario, once the user attaches the properly alignedsensor cartridge 110 to the tissue site and applies the sensor 120 asdiscussed above, medical personnel take a measurement of one or morephysiological parameter of the patient using the sensor 120. The patientthen removes the tissue site from the sensor 120 along with the attachedcartridge 110 as discussed and the patient or medical personnel maydispose of the cartridge 110. Those of skill in the art will recognizefrom the disclosure herein various ways of using the cartridge 110. Forexample, the cartridge 110 of certain embodiments may be mated with thesensor 120 before application to the tissue site. Moreover, thecartridge may be used more than once. For example, the cartridge 110 maybe used several times by the same patient before disposal. In someembodiments, the cartridge 110 may be sterilized between uses.

In certain embodiments, the sensor cartridge 110 is configured to be inelectrical communication with the sensor 120. For example, the sensorcartridge 110 can also include one or more electronic components 130 andone or more coupling portions (not shown) which may be electricallycoupled to the sensor 120. For example, the coupling portions maycomprise one or more electrical contacts (e.g., solder pads), electricalconnectors (e.g., a socket and pin type connector), and the like. Theelectronic components 130 may include one or more information elementsin certain embodiments. The information element may comprise one or morememory devices, such as, for example, one or more EPROMs or EEPROMs(e.g., those commercially available from Dallas Semiconductor), othermemory or processing devices, combinations of the same, or the like. Insome embodiments, the information element includes a conductor, aresistor, a single wire addressable memory device, or the like. Ingeneral, the information element may include a read-only device or aread and write device. The information element may advantageouslycomprise a resistor, an active network, or any combination of theforegoing. The information element may include data accessible by thesensor 120 and/or attached patient monitor to accomplish qualitycontrol, use monitoring, combinations of the same, or the like. Forexample, the information element may provide identification informationto the system (e.g., the sensor 120 and/or monitor) which the systemuses to determine whether the cartridge is compatible with the system.In an advantageous embodiment, the monitor reads the information elementto determine one, some or all of a wide variety of data and information,including, for example, a type of patient, cartridge manufacturerinformation, life data indicating whether the cartridge has been usedand/or should be replaced, encryption information, keys, indexes to keysor has functions, or the like monitor or algorithm upgrade instructionsor data, some or all of parameter equations, information about thepatient, age, sex, medications, and other information that can be usefulfor the accuracy or alarm settings and sensitivities, trend history,alarm history, sensor life, or the like.

The information element may be positioned on the hinge portion 112. Forexample, in one embodiment the information element be embedded in thecartridge 112 material of the hinge portion 112 and is electricallycoupled via a connector extending from the hinge portion 112 which mateswith a corresponding connector on the interior of the sensor 120.Skilled artisans will recognize from the disclosure provided herein avariety of configurations for the placement of the information element.For example, in various embodiments, the information element may belocated on one or more of the inner surface of the cartridge 110, theouter surface of the cartridge 110, or embedded within the cartridge 110material. Moreover, the information element may be positioned on thehinge portion 112, the upper portion 114, the lower portion 116, or acombination thereof.

The information element may advantageously store some or all of a widevariety of data and information, including, for example, information onthe type or operation of the sensor cartridge, buyer or manufacturerinformation, software such as scripts, executable code, or the like,sensor cartridge 110 life data indicating whether the sensor cartridge110 has expired and should be replaced, encryption information, etc. ormonitor or algorithm upgrade instructions or data. In variousconfigurations, the information element may advantageously configure oractivate the monitor, monitor algorithms, monitor functionality, or thelike based on some or all of the foregoing information. For example,without authorized data accessible on the information element, qualitycontrol functions may inhibit functionality of the monitor. Likewise,particular data may activate certain functions while keeping othersinactive. For example, a particular cartridge 110 may be compatible foruse in measuring one type of physiological parameter of a set ofphysiological parameters the monitor is capable of measuring. In such acircumstance, the monitor may only activate measurement of the one typeof physiological parameter based on the data accessible from theinformation element. Further information regarding information elementsand systems and methods for monitoring sensor life can be found in U.S.Publication No. 2008/0088467, which is hereby incorporated in itsentirety by reference herein.

While disclosed with respect to the cartridge 110 of FIGS. 1-2, any ofthe cartridges described herein, such as the cartridges 300, 510, 520,610, 620, 1100, 1200 described below of FIGS. 3-6 and FIGS. 11-12 mayinclude one or more information elements. Likewise, any of the sensorcovers disclosed herein, such as the sensor covers 700, 800 of FIGS.7-10 may include an information element.

FIGS. 2A-D are side hinged-open, side hinged-closed, top-rightperspective and top-left perspective views, respectively, of the sensorcartridge of FIG. 1. As discussed above, the upper portion 114 and lowerportion 116 may be separated such that they rotate about the hingeportion 112 and the cavity 118 becomes large enough to comfortablyreceive the finger (FIG. 2A). Once the finger is placed in the cavity118, the upper and lower portions 114, 116 can be released, coming intocontact with and releasably attaching to the finger (FIG. 2B). The rightand left sides of the cartridge 110 of the illustrated embodiment aresymmetrical. As shown by FIGS. 2C-D, the top and bottom are alsosymmetrical. In other embodiments, the left and right sides and/or thetop and bottom may be shaped differently, such as, for example, toaccommodate asymmetric properties of the finger or other tissue site.

FIGS. 3A-D are side hinged-open and side hinged-closed views, top-rightperspective and top-left perspective views, respectively, of a sensorcartridge 300 according to another embodiment of the disclosure. Thecartridge 300 includes an upper portion 314, a lower portion 316 and ahinge portion 312, which are three separate pieces. As shown, the hingeportion 312 attaches to the back 302 of the upper portion 314 and theback 304 of the lower portion 316, forming a cavity 318 capable ofreceiving a finger of a patient. The hinge portion 312 may attach to theupper and lower portions 312, 314 with glue, may be formed integrallywith the upper and lower portions 312, 314, or may be connected in someother manner. As shown with respect to FIGS. 3C-D, the cartridge 110further includes upper and lower apertures 315, 317, which may besimilar in structure and function to the apertures 115, 117 describedabove with respect to FIGS. 1-2.

FIG. 4 illustrates the mating of the sensor cartridge of FIG. 3 with asensor 420 (shown in a cross-sectional view). The sensor 420 may besimilar in structure and function to the sensor 120 of FIG. 1, forexample, and can include an upper housing 422, a lower housing 424 and ahinge portion 426 which form a cavity 429. One or more securing featuresmay be included on the cartridge 300 to secure the cartridge 300 withthe one or more corresponding securing features on the sensor 420 uponmating to secure the cartridge to the sensor 420 and/or ensure thecorrect position of the cartridge 300 within the sensor 420. Referringto FIGS. 3 and 4, for example, the attachment arm 311 is configured tosecure the cartridge 300 in place when applied to the sensor 420. Uponapplication to a sensor 420 the front portion 425 of the lower housing424 of the sensor 420 may occupy the space defined by the attachment arm311 and the underside of the lower portion 316 of the cartridge 300. Theattachment arm 311 helps to releasably secure the sensor 420, via afriction fit, for example. One or more other features, such as the lip313 disposed on the upper portion 314 of the cartridge 300 can beincluded to further secure the cartridge 300 in the sensor 420. Uponinsertion of the cartridge 300 into the sensor 420, the front portion423 of the upper housing 422 abuts the lip 313. Accordingly, the lip 313can help ensure that the cartridge 300 is positioned appropriately deepwithin the sensor 420.

The shape of the cartridge 300 may be configured to secure the cartridge300 and/or ensure proper positioning of the cartridge 300 upon matingwith the sensor 420. For example, as shown in FIGS. 3-4, the upperportion 314 and/or the lower portion 316 can be sloped such that theythicken towards the front 301 of the cartridge 300. Upon insertion, thesloping feature can provide a friction fit with the correspondingportions of the sensor 420.

As will be appreciated by skilled artisans from the disclosure providedherein, various attachment and positioning mechanisms may be used. Forexample, the attachment arm 311 may further include a protrusion orother feature which may fit into a corresponding feature, such as arecess (not shown), on the underside of the lower housing 424 of thesensor 420. In other configurations, the features may be reversed. Forexample, the protrusion may be on the lower housing 424 and the recessmay be included on the attachment arm 311 of the cartridge 300.

FIGS. 5A-B illustrate side views of two sensor cartridges 510, 520 ofdiffering sizes according to embodiments of the disclosure. The sensorcartridges 510, 520 may be similar in structure and function to thecartridge 100 of FIGS. 1-2 and include upper portions 514, 524, lowerportions 516, 526, hinge portions 512, 522, cavities 518, 528, upperapertures 515, 525 and lower apertures 517, 527, respectively. Thecartridges 510, 520 are configured to configured to accommodatetreatment sites of various sizes, such as for both adult and pediatricapplications. For example, the length L₁ of the cartridge 510 of FIG. 5Ais larger than the corresponding length L₄ of the cartridge 520 of FIG.5B. Additionally, the upper and lower apertures 515, 517 of thecartridge 510 of FIG. 5A are set back a length L₂ from the rear of thecartridge 510 which is relatively large in comparison to the length L₅that the upper and lower apertures 525, 527 of cartridge 520 of FIG. 5Bare set back from the rear of the cartridge 520. The length L₃ of theupper and lower apertures 515, 517 of the cartridge 510 of FIG. 5A isrelatively large in comparison to the length L₆ of the upper and lowerapertures 525, 527 of the cartridge 520 of FIG. 5B.

The cartridge 510 is configured accommodate a larger finger than thecartridge 520. For example, the cartridge 510 may be used in adultapplications and the cartridge 520 may be used in pediatricapplications. A pediatric patient, for example, may have a nail bed thatis set back a relatively short distance from the tip of the finger incomparison to an adult patient. As such, the shorter set back length L₅may be appropriate for a pediatric patient while the length L₂ may beappropriate for an adult patient. A pediatric patient may also have arelatively smaller nail bed than an adult patient such that the smallerlength L₆ appropriately accommodates a pediatric patient while thelength L₃ may more appropriately accommodate an adult patient. Finally,pediatric patients typically have shorter fingers than adult patientssuch that the shorter overall cartridge length L₄ may be appropriate fora pediatric patient while the longer length L₁ may be more appropriatefor adult patients.

As shown, the external profile of the cartridges 520, 521, characterizedin part by the maximum height of the cartridges 520, 521 H₁ may be thesame. As such, the cartridges 520, 521 may mate with a single sizedsensor, thereby reducing cost and complexity. One of skill in the artwill recognize from the disclosure herein other configurations. Some ofthe lengths which are shown as different in the embodiments 510, 520 ofFIGS. 5A-B may be the same in alternative configurations. For example,in various embodiments, one or more of the pairs of lengths L1 and L4,L2 and L5, L3 and L6 may be the same.

FIGS. 6A-B illustrate side views of two sensor cartridges 610, 620 ofdiffering sizes according to embodiments of the disclosure. The sensorcartridges 610, 620 may be similar in structure and function to thecartridge 300 of FIG. 3 and include upper portions 614, 624, lowerportions 616, 626, hinge portions 612, 622, cavities 618, 628,attachment arms 611, 621 and lips 613, 623 respectively. The cartridges610, 620 are configured to configured to accommodate treatment sites ofvarious sizes, such as for both adult and pediatric applications. Forexample, the upper and lower portions 614, 616 of the cartridge 610 arethinner than the corresponding portions 624, 626 of the cartridge 620and define a relatively large cavity 618, characterized in part by thelength H₂. On the other hand, the upper and lower portions 624, 626 ofthe cartridge 620 are relatively thick and define a relatively smallcavity 628, characterized in part by the length H₃. As such, thecartridge 610 is configured accommodate a larger finger than thecartridge 620. For example, the cartridge 610 may be used in adultapplications and the cartridge 620 may be used in pediatricapplications.

As shown, the external profile of the cartridges 620, 621, characterizedin part by the maximum height of the cartridges 620, 621 H₁ may be thesame. As such, the cartridges 620, 621 may mate with a single sizedsensor, thereby reducing cost and complexity. One of skill in the artwill recognize from the disclosure herein other configurations. In someembodiments, the hinge portions 612, 614 are also shaped to accommodatetissue sites of various sizes. In some configurations, the upperportion, the lower portion and/or the hinge portion of the sensorcartridge are constructed of a resilient material (e.g., a spongymaterial) which conforms to the shape of the finger such that a sensorcartridge of a single size can accommodate tissue sites of multiplesizes. In some embodiments in which the opening of the cartridge isgenerally circular, the circumference of the opening through which thepatient inserts their finger into the cavity 518 is larger than theopening of the cartridge 528.

FIGS. 7-8 illustrate two embodiments of a sterile cover 700, 800 eachadvantageously configured to enclose a reusable sensor 120 (FIG. 1). Inthis manner, a patient's tissue site, such as a finger, can be insertedinto the sensor and a physiological measurement made withoutcontamination of the sensor or the patient. The sensor and the patientare thus advantageously protected from exposure to infectious agentssuch as MRSA.

As shown in FIG. 7, a boot-shaped cover 700 defines an enclosure havinga generally tubular leg 720 and a smaller, generally tubular foot 730both extending from a cross-member 710. In some embodiments, thecross-member 710 is sealed or substantially sealed. The leg 720 has anopen end 722 of sufficient diameter to receive a reusable sensor 120, asdescribed with respect to FIGS. 9A-B, below. The foot 730 has a closedend 732 of sufficient diameter to receive the lower housing 124 of areusable sensor 120, as described with respect to FIGS. 9C-D, below. Atie 740 wraps around the open end 722 so as to close that end around thesensor cable 128. In one embodiment, the tie 740 is a self-adhesive tie,for example. In an embodiment, the tie 740 wraps around the open end 722so as to seal the end around the sensor cable 128. A gap 750 between theleg 720 and foot 730 of the cover 700 defines a space configured toaccommodate a finger-tip within the sensor 120.

As shown in FIG. 8, a tube-shaped cover 800 defines an enclosure havinga generally cylindrical body 810 with an open end 812 and a closed end814. The open end 812 is of sufficient diameter to receive first thelower housing 124 followed by the upper housing 122 of a reusable sensor120, as described with respect to FIGS. 10A-D, below. A self-adhesivestrip 820 disposed internal to the body 810 proximate the open end 812closes the open end 812 around the sensor cable 128. In one embodiment,for example, the open end 812 forms a seal around the sensor cable 128.In an embodiment, the covers 700, 800 include of an opticallytransparent or substantially transparent material so as to negligiblyattenuate or otherwise negligibly distort those wavelengths in the redand infrared spectrum utilized in pulse oximeters or otherwise for themeasurement of blood constituents. For example, the covers 700, 800 maybe substantially optically transmissive.

As used herein, the term “tube” is used to describe a generally elongatemember comprising a cavity and may include an open end and a closed end,for example. As used herein, a tube may have a variety of shapes andcharacteristics. For example, the tube 800 of various may comprise acylindrical, rectangular, ovular, triangular, or some othercross-sectional shape, or may be generally deformable.

FIGS. 9A-F illustrate the use of a sterile cover 700 embodiment toenclose a reusable sensor 120, thereby advantageously protecting thesensor from contamination and the patient from exposure to infectiousagents. A reusable sensor 120 in its normally closed position isinitially inserted into the open end 722 of the cover 700 (FIG. 9A). Thesensor 120 is then pushed through the length of the leg 720 until, forexample, the sensor abuts the wall of the cross-member 710 (FIG. 9B).The sensor grips 123, 125 are pressed from outside the cover 700 so asto move the sensor 120 to its open position (FIG. 9C). While maintainingpressure on the grips 123, 125, the sensor lower housing 124 slides intothe foot 730 until it abuts the closed end 732 (FIG. 9D). Pressure isreleased from the grips 123, 125 so that the sensor 120 returns to itsclosed position over the gap 750 (FIG. 9E). The tie 740 is wrappedaround the leg 720 so as to close-off the end 722 tightly around thesensor cable 128 (FIG. 9F). The covered sensor 120 is now ready forsingle-patient use by squeezing the grips 123, 125 to open the sensorand by inserting a patient finger into the cover gap 750, which is nowdisposed inside the sensor 120, between the emitters and detector.

FIGS. 10A-E illustrate the use of another sterile cover 800 embodimentto enclose a reusable sensor 120, likewise substantially protecting thesensor and patient from contamination and/or infectious agents. Sensorgrips 123, 125 are pressed to place the sensor 120 in an open position(FIG. 10A). The cover 800 may be initially in an “accordion” state orotherwise folded, rolled or compressed, or otherwise collapsible to areduced overall length. The cover opening 812 is slipped over the lowerhousing 124 (FIG. 10A). Maintaining the sensor 120 in the open position,the cover 800 is unfolded or otherwise extended in length as the opening812 is pulled over the grips 123, 125 and onto the upper housing 122(FIG. 10B). The cover opening 812 is pulled further along the upperhousing 122 and onto the sensor cable 128 (FIGS. 10C-D). The sensorgrips 123, 125 are released so that the sensor 120 returns to itsnormally closed position (FIG. 10E). The self-adhesive strip 820 justinside the opening 812 is then exposed, such as by peeling back andremoving a liner, and the opening 812 is securely closed around thecable 128 (FIG. 10E). The covered sensor 120 is now ready forsingle-patient use by squeezing the grips 123, 125 to open the sensorand by inserting 850 a patient finger into the sensor between the foldedover wall 810 portions of the cover 800 (FIG. 10E). This places thepatient's fingertip inside the sensor 120, between the emitters anddetector.

Skilled artisans will recognize a variety of alternatives sensor covers700, 800 from the disclosure provided herein. For example, in otherembodiments, the covers 700, 800 may include one or more apertures suchas one or more of the apertures described herein. The covers 700, 800may comprise a rigid or semi-rigid material. Moreover, the covers 700,800 may be used in addition to a cartridge such as one or more of thecartridges described herein with respect to FIGS. 1-6 and 11-12. In onealternative embodiment, the cover 700, 800 may extend beyond the sensor120 along some length of the cable 128. For example, the cover 700, 800may extend substantially along the entire cable to the monitor in oneembodiment. In another embodiment, the cover 700, 800 may extendpartially along the cable 128.

FIGS. 11A-B illustrate top front and bottom rear perspective views,respectively, of a sensor cartridge 1100 according to an embodiment ofthe disclosure. In certain circumstances, light incident on the fingerfrom the emitter may not be entirely absorbed by the finger. Inaddition, a certain portion of attenuated light will exit the other sideof the finger. Such portions of light may reflect within the spacebetween the cartridge and the finger or between the cartridge and thesensor. These portions of light can interfere with each other, with theemitted light and/or with the attenuated light. These portions ofreflected light and associated interfering light can be incident on thedetector. This phenomena, sometimes referred to herein as “lightbounce,” can potentially cause inaccurate measurements, depending oncertain factors such as the amount of light bounce and the relativesensitivity of the measured signal.

The sensor cartridge 1100 is configured for application to a tissue sitesuch as a finger, for example. The finger or other tissue site may beplaced in the opening 1102. In addition, the cartridge 1100 isconfigured for insertion into a reusable sensor such as the sensor 120.The sensor cartridge 1100 further includes an upper aperture 1104 and alower aperture 1106. The apertures 1104, 1106 generally allow for propersensor operation. For example, the apertures 1104, 1106 allow for lightfrom one or more emitters of the sensor 120 to contact the finger andfor light attenuated by the tissue site to be received by a detector ofthe sensor 120. The apertures 1104, 1106 may function in a mannersimilar to and provide similar advantages as the apertures 115, 117 ofthe cartridge 110 of FIGS. 1-2. The cartridge may comprise AcrylonitrileButadiene Styrene (“ABS”), other types of rubber or plastic materials,or some other material compatible with the embodiments described herein.

As shown, the sensor cartridge 1100 generally envelopes the finger whenit is applied to the cartridge 1100. Moreover, the cartridge 1100 maycomprise a color absorptive of the light emitted from the emitter of thesensor 120. For example, the cartridge 1100 may comprise a dark materialas shown, such as a substantially black or opaque material. As describedabove, a certain portion of incident on the finger from the emitter ofthe sensor 120 may not be absorbed by the finger, but may instead bereflected off of the finger. In addition, a certain portion ofattenuated light will exit the other side of the finger. Because thecartridge 1100 generally envelopes the finger and is absorptive of theemitted light, light which is not absorbed by the finger or otherwisemay advantageously escape into the region between the cartridge and thefinger will be substantially absorbed by the cartridge 1100 due to itsabsorptive properties, reducing the effect of light bounce.

Alternative configurations of the cartridge 1100 are possible as will berecognized by skilled artisans from the disclosure herein. For example,the cartridge 1100 body may comprise a substantially thin rubbermaterial in some embodiments. The cartridge 1100 may include an adhesiveproximate the perimeter of the opening 1102, such as the self-adhesivestrip 820 of the cartridge 800 of FIG. 8, which may help create a sealbetween the finger and the cartridge 1100. In other configurations, theperimeter of the opening may include an elastic band capable of creatingan elastic seal between the finger and the cartridge 1100. In certainembodiments, the cartridge 1100 or a portion thereof may include adifferent color such as a relatively light color, or may be translucentor partially translucent. In one configuration, the interior of thecartridge 1100 comprises a substantially dark color and the outersurface comprises another color, such as a light color. In yet anotherembodiment, the interior of the cartridge 110 comprises a substantiallylight color and the outer surface comprises a substantially dark color.

FIGS. 12A-B illustrate top front and bottom rear perspective views,respectively, of a sensor cartridge according to another embodiment ofthe disclosure. The cartridge 1200 of FIG. 12 may be generally similarin structure and function to the cartridge 1100 of FIG. 11. For example,the cartridge 1200 includes an opening 1202, a cavity 1208, an upperaperture 1204 and a lower aperture 1206. In addition, the cartridge 1200comprises a color absorptive of the emitted light and advantageouslyreduces the effect of light bounce.

The cartridge 1200 may not fit in a uniformly snug manner with the upperand lower sensor housings 122, 124. For example, as the upper and lowersensor housings 122, 124 exert force directly on the outer surface ofthe cartridge 1200 and thus indirectly on the tissue site within thecartridge 1200, the sensor cartridge 1200 may flex and partially deformin response to this force. This flexing may create gaps between portionsof the inner surfaces of the upper and lower sensor housings 122, 124and the outer surface of the cartridge 1200. The cartridge 1200 includesconnecting portions 1210, 1212 which are configured to bridge potentialgaps between the outer surface of the cartridge 1200 and the innersurfaces of the upper and lower sensor housings 122, 124. Particularly,the connecting portions 1210, 1212 are configured to bridge these gapssubstantially in the region of the perimeter of the apertures 1204,1206, respectively. The connecting portions 1210, 1212 thereby create aseal between the perimeter of the apertures 1204, 1206 and the innersurfaces of the upper and lower sensor housings 122, 124, respectively.Channel regions are thus created whereby light from the emitter cantravel from the emitter to the aperture 1204 and whereby attenuatedlight can travel from the tissue site to the detector. Thus, theconnecting portion 1210 prevents light directed towards the upperaperture 1204 from the emitter from escaping into the region between thebetween the inner surface of the upper sensor housing 122 and the outersurface of the cartridge 1200. Likewise, the connecting portion 1212prevents attenuated light exiting the tissue site towards the detectorof the sensor 120 from prevented from escaping into the region betweenthe inner surface of the lower sensor housing 124 and the cartridge1200. Because light escaping into these regions may contribute to lightbounce, as described above, the connecting portions 1210, 1212advantageously provide further reduction of light bounce. Moreover, theconnecting portions 1210, 1212 generally cause a greater percentage oflight from the emitter to be directly incident on the tissue site and acause greater percentage of attenuated light exiting from the tissuesite to be directly incident on the detector. The connecting portions1210, 1212 thus can provide for increased measurement accuracy, improvedcalibration and efficiency of sensor operation, among other advantages.

The connecting portions 1210, 1212 of the illustrated embodiment includefour panels each extending from one side of the perimeter of the upperand lower apertures 1204, 1206 to form raised rectangular borders aroundthe apertures 1204, 1206. The connecting portions 1210, 1212 areconfigured to contact the interior surfaces of the upper and lowersensor housings 122, 124 around the emitter and the detector,respectively. The connecting portions 1210, 1212 include a flexiblematerial such as a rubber or plastic which conforms to the interiorsurfaces of the upper and lower sensor housings 122, 124, respectively.As such, the connecting portion 1210 helps to create a seal between theemitter of the sensor 120 and the cartridge as described above, therebyreducing light bounce and providing for increased measurement accuracy.Likewise, the connecting portion 1212 helps to create a seal between thedetector of the sensor 120 and the cartridge 1200 as described above,thereby further reducing light bounce and improving measurementaccuracy.

As will be appreciated by those of skill in the art from the disclosureprovided herein, alternative configurations of the cartridge 1200 arepossible. For example, in certain embodiments, one or more of theconnecting portions 1210, 1212 may comprise a rigid material. Theconnecting portions 1210, 1212 may mate with corresponding features ofthe interior surfaces of the upper and lower sensor housings 122, 124,respectively. For example, the connecting portions 1210, 1212 may formraised features such as in the illustrated embodiment which fit intocorresponding female portions, such as recesses in the interior surfacesof the sensor housings 122, 124. In various embodiments, snap-fit,friction-fit, and other mating mechanisms may be employed. Certainfeatures may be reversed in some embodiments. For example, one or moreof the interior surfaces of the sensor housings 122, 124 may includemale portions and the connecting portions 1210, 1212 may include femaleportions. In certain embodiments, connecting portions such as theconnecting portions 1210, 1212 may be used on other cartridges describedherein, such as, for example, the cartridge 110 of FIGS. 1-2, or thecartridge 300 of FIG. 3.

Various sensor cartridges and covers have been disclosed in detail inconnection with various embodiments. These embodiments are disclosed byway of examples only and are not to limit the scope of the claims thatfollow. One of ordinary skill in the art will appreciate the manyvariations, modifications and combinations. For example, in oneembodiment, the cartridge 110 of FIG. 2 includes a securing feature suchas the securing feature 311 of the cartridge 300 of FIG. 3. In someembodiments, the cartridges 110, 300 of FIGS. 2 and 3 are configured tosubstantially envelope the tissue site in a manner similar to thecartridges 1100, 1200 of FIGS. 11 and 12. In various embodiments, any ofthe cartridges described throughout the disclosure, such as thecartridges 300, 510, 610, 1100, 1200 described with respect to FIGS. 3,5, 6, 11 and 12, may include a film covering the respective apertures.For example, the film may include a film such as the one described abovewith respect to the apertures 115, 117 of the cartridge 110 of FIGS.1-2. In addition, in various embodiments the sensor cartridges andcovers are used with a sensor that may measure any type of physiologicalparameter. In various embodiments, the sensor cartridges and covers maybe for any type of medical device.

1. (canceled)
 2. A disposable sterile barrier that interposes a materialimpermeable to infectious biological substances between a tissue siteand surfaces of a sensor configured to grasp the tissue site, the sensorconfigured to transmit optical radiation into the tissue site and togenerate a signal responsive to the optical radiation after attenuationby pulsatile blood flow within the tissue site, the disposable sterilebarrier comprising: an optically transparent material that issubstantially impermeable to infectious biological substances; a firstportion of the material formed such that the first portion can beinterposed between a tissue site and a first surface of a reusableoptical sensor proximate an emitter of the sensor; and a second portionof the material formed such that the second portion can be interposedbetween the tissue site and a second surface of the sensor proximate adetector of the sensor.
 3. The disposable sterile barrier of claim 2,wherein: the material is pre-formed into an elongate cover membercomprising a cavity, an open end and a closed end and configured to beplaced over the reusable optical sensor and over at least a portion of asensor cable extending from the sensor, and the cover member comprises afastener proximate the open end of the cover member, the fastenerconfigured to close the open end of the cover member around the sensorcable.
 4. The disposable sterile barrier according to claim 3, whereinthe cavity of the elongate cover member is capable of accommodating afirst sensor housing comprising one of the first and second surfaces andto accommodate a second sensor housing comprising the other of the firstand second surfaces so as to enclose the sensor within the cavity. 5.The disposable sterile barrier of claim 2, wherein the disposablesterile barrier comprises a cartridge capable of being placed on thetissue site and then inserted into the reusable optical sensor so as tomake physiological measurements of blood flow within the tissue site. 6.The disposable sterile barrier of claim 2, wherein the tissue site is atleast a portion of a finger.
 7. An optical sensing method ofnon-invasively measuring the constituents of pulsatile blood flow withina tissue site without substantial risk nosocomial infection by directcontact between a sensor and the tissue site, the optical sensing methodcomprising: providing a reusable optical sensor having an emitterdisposed within a first housing and a detector disposed within a secondhousing, the emitter and detector in communication with a sensor cable,the first and second housings configured to be urged against oppositesides of a tissue site upon application of the sensor to the tissuesite, the emitter configured to transmit optical radiation having one ormore predetermined wavelengths into the tissue site and the detectorconfigured to receive the optical radiation after attenuation by thetissue site, the sensor configured to generate one or more signalsindicative of the attenuated radiation, the one or more signalstransmitted via the sensor cable to a monitor configured to process theone or more signals to determine one or more physiological parameters ofpatient; and applying a barrier so as to make physiological measurementswithout direct contact between the tissue site and the sensor, thebarrier interposed between the tissue site and the first housing andinterposed between the tissue site and the second housing uponapplication of the tissue site to the sensor, the barrier comprisingmaterial substantially impermeable to infectious substances andsubstantially transparent so as not to substantially distort thephysiological measurements.
 8. The optical sensing method of claim 7,further comprising disposing of the barrier after completing thephysiological measurements.
 9. The optical sensing method of claim 7,wherein applying comprises: providing a boot-shaped sensor covercomprising a leg portion and a foot portion; fitting the sensor throughan open end of the cover; positioning the sensor within the boot-shapedcover such that one of the first and second housings is within the legportion and the other of the first and second housings is within thefoot portion; and sealing the open end of the cover around the sensorcable.
 10. The optical sensing method of claim 7, wherein applyingcomprises: providing a collapsible tube comprising an open end and aclosed end; expanding the tube from a collapsed state to an un-collapsedstate; fitting the open end of the tube around one of the first sensorhousing and the second sensor housing; moving the open end firstly alongone of the first and second housings and then along the other of thefirst and second housings such that the sensor and at least a portion ofthe sensor cable are enclosed within the tube; and sealing the open endaround the sensor cable.
 11. The disposable sterile barrier of claim 7,wherein the tissue site is at least a portion of a finger.
 12. Adisposable sterile barrier comprising: an elongate tube comprising acavity, an open end and a closed end, the open end comprising an openinglarge enough to accommodate a reusable optical sensor, the cavity sizedto fully enclose the reusable optical sensor and at least a portion of asensor cable extending from the optical sensor, the elongate tubecomprising a material which is substantially optically transparent andsubstantially impermeable to infectious biological substances; and afastener disposed proximate the open end of the elongate tube andconfigured to seal the open end of the elongate tube around the sensorcable.